Alternators with claw-pole rotor arrangements (also known as “Lundell” type rotors) are commonly used in light-duty and heavy-duty vehicle applications. These alternators include a claw-pole rotor, a stator, a rectifier and a voltage regulator. The rotor is comprised of a field coil wound over an iron core and two opposing claw-pole iron segments surrounding the field coil. Each claw-pole iron segment typically includes six to nine fingers that are interlaced with the same number of fingers from the opposing claw-pole iron segment. When current flows through the field winding, one of the claw-pole segments provides a magnetic north segment and the other provides a magnetic south segment. Thus, the interlaced fingers of the claw-pole configuration result in a rotor with an alternating N pole, S pole arrangement.
Rotation of the rotor provides a rotating magnetic field. This rotating magnetic field induces a voltage in the windings positioned on the stator. The magnetic field in the stator rotates at the same speed, or synchronously, with the rotor field. The stator windings are connected to the rectifier, which converts the AC stator output to a DC output. At the same time, the voltage regulator monitors the system voltage and adjusts the output of the alternator by controlling the current through the field coil.
During operation of the claw-pole alternator, the alternator must be cooled to maintain the efficiency and performance of the alternator. The alternator is typically cooled by air flowing through the alternator, and it is generally desirable to direct as much cooling air as possible through the alternator. Air flow through the alternator is generally urged by a fan at the front of the alternator that acts to lower the air pressure within the alternator and draw cooling air into the alternator. Air flows from the rear of the alternator to the front of the alternator where it is expelled by the fan. The air expelled from the alternator is combined with the under hood airflow in the vehicle. This under hood vehicle airflow is generally from the front of the vehicle to the rear due substantially to the forward movement of the vehicle and the action of radiator cooling fans disposed at the front of the vehicle. Thus, the heated air expelled from the alternator, combines with the under hood airflow, and is carried back to the rear of the alternator where at least a portion of the heated air is re-circulated through the alternator.
In view of the foregoing, it would be desirable to provide an alternator arrangement having an improved airflow arrangement capable of directing an increased volume of cooling air through the alternator. It would also be desirable if such improved airflow arrangement could be accomplished simply without adding a significant number of additional components to the alternator. It would also be desirable if such improved airflow arrangement could be achieved without disturbing the arrangement of components within the alternator or significantly affecting electrical and magnetic performance of the alternator.